Organic thin film transistor manufacturing method and organic thin film transistor

ABSTRACT

Provided are an organic TFT manufacturing method whereby flow of ink into an unnecessary area can be suppressed and excellent characteristics and high reliability can be obtained, and an organic TFT. The organic TFT manufacturing method comprises a step of providing a source electrode and a drain electrode on a base member; a step of providing a bank layer, which has an opening on a channel between the source electrode and the drain electrode, an opening on a predetermined area of the base member, and a groove or grooves around the opening on the predetermined area, which surround the opening on the predetermined area; and a step of supplying an organic semiconductor solution to the opening of the bank layer formed on the channel to form an organic semiconductor layer.

RELATED APPLICATIONS

This application is a U.S. National Stage Application under 35 U.S.C.371 of International Application No. PCT/JP2009/067627, filed with theJapanese Patent Office on Oct. 9, 2009, which claims priority toJapanese Patent Application No. 2008-295427, filed Nov. 19, 2008.

TECHNICAL FIELD

The present invention relates to an organic thin film transistormanufacturing method, and to an organic thin film transistor.

TECHNICAL BACKGROUND

In recent years, technique for forming a thin film transistor(hereinafter also referred to as TFT) on a basal plate has greatlyprogressed. Particularly, its application to a driving element of anactive matrix type large screen display has been developed. A TFT, whichhas currently been put to practical use, is manufactured employing a Sibased inorganic material such as a-Si or poly-Si. However, themanufacture of a TFT employing such an inorganic material requires avacuum process or high temperature process, which has a great influenceon the manufacture cost.

In order to solve the problem as described above, a TFT employing anorganic material (hereinafter also referred to as organic TFT) has beenintensively investigated in recent years. Organic materials have a widechoice of materials as compared to inorganic materials. Further, in themanufacturing process of an organic TFT, a process such as printing orcoating, which is excellent in productivity, is used instead of thevacuum process or the high temperature process as described above,whereby the manufacturing cost can be suppressed. Further, an organicTFT can be formed on a less heat resistant basal plate such as a plasticfilm basal plate and its application to many fields has beeninvestigated.

As a coating method of an organic semiconductor material, there is knowna liquid droplet coating technique such as an ink jet process or adispenser method, in which direct coating of a solution containing anorganic semiconductor material (hereinafter also referred to as ink) iscarried out. There are advantages in these techniques that (1) a vacuumprocess is not required, (2) waste of materials is reduced, and (3)since direct patterning is possible, an etching process as carried outin photolithography is unnecessary. These techniques can suppress themanufacturing cost, and have been intensively investigated in variousfields.

In order to obtain excellent electric properties and high reliability insuch an organic TFT, it is necessary that an organic semiconductor layerbe formed in an appropriate thickness and precisely at a pre-determinedposition. However, when an organic semiconductor layer of an organic TFTis formed using the ink jet process or the dispenser method as describedabove, in some cases a jetted ink wet-spreads on a basal plate due tothe influence of surface conditions of the basal plate, ambientatmosphere or the like, and reaches an unnecessary area before the inkis dried to solidify. In such a case, there occurs problem that patterndefect is produced, a sufficient thickness is not obtained, and as aresult, an organic TFT with good characteristics cannot be obtained.

In order to solve the problem above, various techniques have beeninvestigated. For example, a technique is known in which a partitionwall called a bank is formed around an area to be coated so that thewall prevents jetted ink from flowing outside the area to be coated(Patent Document 1).

However, the effect of preventing jetted ink from flowing outside thearea to be coated is not sufficient in the bank disclosed in PatentDocument 1. The reason is as follows.

1. Ink Solvent

An organic semiconductor material is ordinarily low in solubility, andeven a precursor material, in which solubility is increased, is solubleonly in an organic solvent. The organic solvent is poor in theintermolecular interaction and generally low in the surface tension, ascompared to water (73 mN/m). The surface tension of an organic solventis as follows, for example, methanol: 23 mN/m; ethanol: 23 mN/m;isopropyl alcohol: 21 mN/m; acetone: 23 mN/m; benzene: 29 mN/m;n-hexane: 18 mN/m; n-pentane: 16 mN/m; monomethyl ether acetate (PGMEA):24 mN/m; and anisole: 33 mN/m

Accordingly, ink of an organic semiconductive material employing anorganic solvent is likely to wet the bank, and is difficult to controlits flow.

2. Ink Concentration

Solubility of an organic semiconductive material is ordinarily less than1%, and at most around several percent. Therefore, in order to secure arequired thickness of an organic semiconductor layer it is necessary tocoat a large amount of ink. Consequently, it is not easy to prevent theink flow via a bank.

3. Ink Coating Region

A channel, where an organic semiconductor layer is to be formed, has atmost a size of 30 μm (short side)×100 μm (long side), and ordinarily asize of 10 μm (short side)×30 μm (long side). On the other hand, thesize of ink droplets jetted by means of an ink jet process is 10 to 20μm Φ. Therefore, when deposition accuracy of the ink droplets or patternforming accuracy of the channel is taken into account, the ink droplets,after deposition to the channel, spread on the bank. That is, it isdifficult to prevent the undesired ink flow by means of a bank.

In order to solve the above problem, a method is known in which theshape of the bank is improved and an opening is formed both on thechannel and on an ink guide region extending outward from the channel,whereby the ink is introduced into the channel through the ink guideregion (Patent Document 2).

PRIOR ART LITERATURES Patent Documents

Patent Document 1: Japanese Patent No. 3692524

Patent Document 2: Japanese Laid Open Patent Publication No. 2007-142435

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, the method disclosed in Patent Document 2 has problem in thatalthough it can introduce the ink into the channel, it cannot preventflow of the ink into an area, which the ink is not to flow into.

For example, in a display equipped with an organic TFT, there are somecases in which multiplication of a TFT, multiple layer formation of eachof a TFT and a pixel electrode, and the like are necessary, and acontact hole, through which a predetermined electrode disposed in theupper layer of the multilayer is connected to that in the lower layer ofthe multilayer is formed. When the ink flows into and deposits on such acontact hole, there is problem in that connection fault occurs, and agood display image cannot be obtained. Thus, a technique has beenrequired in which the flow of ink into an area into which the ink is notto flow is suppressed.

In view of the above, the present invention has been made, and an objectof the invention is to provide a method of manufacturing an organic TFTwhereby flow of ink into an unnecessary area can be suppressed andexcellent characteristics and high reliability can be obtained, and toprovide an organic TFT.

Means for Solving the Above Problems

The above object of the invention can be attained by any one of theinventions described in the following items 1 through 11.

1. A method of manufacturing an organic thin film transistor, featuredin that it comprises a step of providing a source electrode and a drainelectrode on a base member; a step of providing a bank layer, which hasan opening on a channel between the source electrode and the drainelectrode, an opening on a predetermined area of the base member, and agroove or grooves around the opening on the predetermined area, whichsurround the opening on the predetermined area; and a step of supplyingan organic semiconductor solution to the opening of the bank layerformed on the channel to form an organic semiconductor layer.

2. A method of manufacturing an organic thin film transistor of item 1above, featured in that the supplying of the organic semiconductorsolution is carried out employing an ink jet process.

3. A method of manufacturing an organic thin film transistor of item 1or 2 above, featured in that a material for the bank layer is repellentagainst the organic semiconductor solution.

4. A method of manufacturing an organic thin film transistor of any oneof items 1 through 3 above, featured in that a plurality of the groovesare formed.

5. A method of manufacturing an organic thin film transistor of any oneof items 1 through 4 above, featured in that the predetermined area isan area, extending from the source electrode or the drain electrode, inwhich a connecting terminal is provided.

6. A method of manufacturing an organic thin film transistor of item 5above, featured in that it further comprises a step of forming a pixelelectrode to be connected with the connecting terminal through theopening of the bank layer formed on the predetermined area.

7. A method of manufacturing an organic thin film transistor of any oneof items 1 through 6 above, featured in that it further comprises a stepof forming a passivation layer on the organic semiconductor layer.

8. A method of manufacturing an organic thin film transistor of any oneof items 1 through 7 above, the organic thin film transistor being of abottom gate type structure, featured in that the base member comprises abasal plate, a gate electrode formed on the basal plate and a gateinsulation layer covering the gate electrode.

9. A method of manufacturing an organic thin film transistor of item 8above, featured in that it comprises providing a wiring pattern underthe gate insulation layer to form the groove or grooves, wherein thethickness of the wiring pattern partially raises the surface of the gateinsulation layer, thereby partially raising the surface of the banklayer formed on the gate insulation layer.

10. A method of manufacturing an organic thin film transistor of any oneof items 1 through 6 above, the organic thin film transistor being of atop gate type structure, featured in that the base member is a basalplate.

11. An organic thin film transistor manufactured employing the organicthin film transistor manufacturing method of any one of items 1 through10 above.

Effects of the Invention

In the invention, even when the ink supplied into the channel flowsbeyond the bank, the flow of the ink into a predetermined area intowhich the ink is not to flow is prevented by the groove provided aroundthe predetermined area. As a result, an organic TFT with excellentcharacteristics and high reliability can be manufactured.

BRIEF EXPLANATION OF THE DRAWINGS

FIGS. 1 a, 1 b, 1 c, 1 d-1, 1 d-2, 1 e, 1 f, and 1 g show sectionalschematic views and a plan schematic view, demonstrating a manufacturingmethod of a bottom gate type organic TFT in the embodiment of theinvention.

FIGS. 2 a and 2 b show sectional schematic views explaining function ofa bank layer.

FIG. 3 shows a sectional schematic view demonstrating a constitution ofa top gate type organic TFT in the embodiment of the invention.

FIG. 4 shows a sectional schematic view demonstrating another embodimentof a groove formation method.

PREFERRED EMBODIMENT OF THE INVENTION

Next, the preferred embodiment of the organic TFT manufacturing methodand the organic TFT of the present invention will be explained withreference to drawings. The invention will be explained based on theembodiment illustrated in the drawings, but is not specifically limitedto the embodiment.

A bottom gate type organic TFT manufacturing method of the invention,which is one of the embodiments of the invention, will be explained withreference to FIG. 1. FIGS. 1 a through 1 g are sectional views showingan outline of a manufacturing method of a bottom gate type organic TFT1.

Firstly, a gate electrode G is formed on a basal plate P (FIG. 1 a). Asa material for the basal plate P, there can be used polyimide,polyamide, polyethylene terephthalate (PET), polyethylene naphthalate(PEN), polyester sulfone (PES), glass, and the like.

The gate electrode G can be formed on a basal plate P by forming a filmof a gate electrode material on the basal plate P employing a sputteringmethod or a vapor deposition method and then subjecting the film topatterning employing a photolithographic method. As a material for thegate electrode G, there can be used Al, Au, Ag, Pt, Pd, Cu, Cr, Mo, In,Zn, Mg, and their alloys or oxides, and organic conductive materialssuch as carbon nanotubes.

Subsequently, a gate insulation layer IF is formed (FIG. 1 b). The gateinsulation layer IF can be formed according to a sputtering method, avapor deposition method or a CVD method. As a material for the gateinsulation layer IF, there can be used inorganic oxides such as siliconoxide, aluminum oxide, tantalum oxide and titanium oxide; inorganicnitrides such as silicon nitride and aluminum nitride; and organiccompounds such as polyimide, polyamide, polyester, polyacrylate, aphotoradical or photocationic polymerization type photocurable resin, acopolymer containing an acrylonitrile component, polyvinyl phenol,polyvinyl alcohol, novolak resin and cyanoethyl pullulan.

Subsequently, a source electrode S and a drain electrode D are formed(FIG. 1 c). After the basal plate P on which the gate insulation layerIF was formed is washed, the source and drain electrodes can be formedaccording to the photolithographic method as described above in theformation of the gate electrode (various printing methods or a liquiddroplet coating method. As a material for the source electrode S and thedrain electrode D, there can be used the same materials as thosedescribed above as the materials for the gate electrode G.

Subsequently, a bank layer BK is formed (FIGS. 1 d-1 and 1 d-2). Herein,FIG. 1 d-2 is a plan schematic view of FIG. 1 d-1, and FIG. 1 d-1 showsa sectional view in dotted line A-B-A′ in FIG. 1 d-2. The bank layer BKcan be formed by forming a film of a bank material employing a spincoating method and then subjecting the film to patterning employing aphotolithographic method. As a material for the bank layer BK, there canbe used a bank material having liquid repellency against an organicsemiconductor solution (ink) IK. Preferred examples of the bank materialinclude acryl resins, polyimide resins and epoxy resins, which areinsoluble in a solvent of ink IK. Particularly when a resin with lightsensitivity is used as the bank material, fine patterning can be carriedout via photolithography. On the other hand, when a resin having nolight sensitivity is used as the bank material, patterning can becarried out using printing technology. Even a resin having no liquidrepellency can be used, as long as the resin contains a liquid repellentcomponent, which oozes on the resin surface to exhibit liquidrepellency.

Herein, the shape of the bank layer BK will be explained. In the banklayer BK, an opening BKa is formed on a channel between the sourceelectrode S and the drain electrode D and an opening BKb is formed on anarea which extends from the drain electrode D and corresponds to aconnecting terminal Da. Further, around the opening BKb formed on thatarea corresponding to the connecting terminal Da is formed a groove BKcsurrounding the opening BKb. Function of the groove BKc will beexplained later.

Next, an organic semiconductor layer SF is formed (FIG. 1 e). Theorganic semiconductor layer SF can be formed using an ink jet processwherein ink IK is jetted into the opening BKa of the bank layer BKformed on the channel.

Examples of a material for the organic semiconductor layer SF includepolycyclic aromatic compounds or conjugated polymers but are notspecifically limited thereto. Materials for the organic semiconductorlayer SF may be high molecular weight materials, oligomers or lowmolecular weight materials, and are preferably those in which themolecules after formation of the film, are regularly aligned due tointermolecular interaction to form a crystal. As the materials for theorganic semiconductor layer SF, there can be used pentacene, porphyrin,phthalocyanine, oligothiophene, oligophenylene, polythiophene,polyphenylene and their derivative. Typical examples thereof includepentacene, 6,13-bis(triisopropylsilylethynyOpentacene,tetrabenzoporphyrin, poly(3-hexylthiophene), and the like.

Use of a solvent with a high surface tension in the ink IK improvesfluidity control property, however, solubility of organic semiconductorlayer materials to the solvent or consistency with the effect due toMarangoni convection or the like during drying process is also animportant factor, and therefore, it is important to maintain a balancebetween factors required during the whole film formation process. As thesolvent, the solvents as described above can be used.

Subsequently, a passivation layer PF is formed which shields or protectsthe organic semiconductor layer SF from ambient atmosphere (FIG. 1 f).This passivation layer PF is formed to cover an area other than theopening BKb in the bank layer BK. As a material for the passivationlayer PF, there can be used SiO₂, SiN and the like. When the passivationlayer PF is formed, a sputtering method can be used, but an atmosphericplasma method is preferably used, since the sputtering method requires avacuum apparatus resulting in high cost. The atmospheric plasma methodcan form a thin film with high density and is suitable for formation ofthe passivation layer PF, which functions as a protective layer for theorganic semiconductor layer SE Herein, the passivation layer PF is notnecessarily needed, and is optionally formed according to kind ofmaterials used in the organic semiconductor layer SF. Thus, an organicTFT 1 is prepared.

Finally, a pixel electrode E is formed on the organic TFT 1 preparedabove (FIG. 1 g), thereby preparing an organic TFT array 1A. In thiscase, the pixel electrode E is connected through the opening BKb formedin the banking layer BK with the connecting terminal Da providedextending from the drain electrode D. The pixel electrode E can beformed by vacuum depositing a pixel electrode material on the organicTFT 1, using a sputtering method, and subjecting the deposited electrodematerial to photolithography. Alternatively, the pixel electrode E canbe formed via direct patterning which is carried out using an IJ processor a printing method. As a material for the pixel electrode, there canbe used ITO and the like.

Next, the groove BKc formed in the bank layer BK will be explained withreference to FIG. 2. FIGS. 2 a and 2 b are schematic sectional views ofthe circumference of the groove BKc for explaining function of thegroove BKc.

The concave-convex surface of the bank layer BK retards a wet-spreadingspeed of ink IK. Particularly when the surface shape of the bank layerBK varies so that the contact angle of the ink IK increases at theboundary between the concavity and convexity, the ink IK is temporarilypinned at a portion at which the surface shape varies.

There are special bank materials having a surface liquid repellency anda section liquid receptivity, however, a general bank material itselfhas ordinarily a liquid repellency (resulting from material), andprovides the same contact angle on the surface and on the cross-sectionsurface. When the ink IK wet-spreads on the surface of the bank layer BK(FIG. 2 a) and arrives at the sidewall (wall of the groove BKc) of thebank layer BK (FIG. 2 b), it behaves in a way that it contacts thesidewall at the same contact angle θ1. The surface of the bank layer BKis flexed in the direction distant from the ink IK by the groove BKc,and an apparent contact angle increases by a flexion angle θ2, enhancingliquid repellency. This makes it possible to allow the ink IK to stay atan intended area. When the thickness of the bank layer BK is not lessthan 50 nm, and preferably not less than 300 nm, then it is possible toincrease the angle θ2, which can obtain greater benefit.

Incidentally, in the above embodiment of the invention, the groove BKcis an opening such that the base member is exposed, but may be simply anindentation. The indentation can provide the same effect as describedabove. Further, a plurality of the grooves BKc surrounding the BKb maybe provided, whereby a greater effect can be achieved.

In the above embodiment of the invention, the groove BKc is formed viapatterning via photolithography. However, as is shown in FIG. 4, thegroove BKc may be formed by providing, under the gate insulation layerIF, a wiring pattern BL, for example, a busline, etc., wherein thethickness of the wiring pattern BL partially raises the surface of thegate insulation layer IF and then partially raises the surface of thebank layer BK formed on the gate insulation layer IF (a raised portionBKt). This reflects the surface shape of the underlying layer such asthe gate insulation layer IF and the like into the surface shape of thebank layer BK, since a layer with a thickness of ordinarily not morethan 1 μm such as the gate insulation layer IF is difficult toplanarize. This method can easily form the groove BKc without employinga photolithographic method, simply by providing a new wiring pattern BLin addition to an existing busline, resulting in simplicity of themanufacturing process and in low cost.

In order to increase the flexion angle θ2 of the bank layer BK or thenumber of grooves BKc, the photolithographic method and the method usingthe wiring pattern as described above may be used in combination to formthe grooves BKc. This combination use of the two methods can exhibit asynergic effect even when use of one method cannot provide a sufficienteffect.

As is described above, in the manufacturing method of the organic TFT 1in the embodiment of the invention, the bank layer BK comprising theopening BKa on the channel, the opening BKb on the area corresponding tothe connecting terminal Da and provided around the opening BKb, thegroove BKc surrounding the opening BKb are formed; and the ink IK issupplied to the opening BKa of the bank layer BK formed on the channelto form the organic semiconductor layer SF.

According to this method, even when the ink IK supplied to the openingBKa on the channel flows over the bank during the formation of theorganic semiconductor layer SF, the flow of the ink IK into an area(such as the connecting terminal Da), into which the ink is not to flow,is prevented by the groove BKc formed around that area. As a result, anorganic TFT 1 with excellent characteristics and high reliability can bemanufactured.

In the embodiment of the invention, the constitution of the bottom gatetype organic TFT 1 has been shown above, but the constitution of theorganic TFT is not specifically limited thereto and may be of a top gatetype structure. In the latter, the bank layer BK is formed on the basalplate P with the source electrode S and the drain electrode D as shownin FIG. 3.

Next, an example of the manufacturing method of a bottom gate bottomcontact type organic TFT 1 in the embodiment of the invention will beexplained with reference to FIG. 1 described above.

EXAMPLE

Firstly, a light sensitive photoresist was coated on a soda lime glassplate (FIG. 1 a: a basal plate P) for an STN liquid crystal with aSiO₂/Cr film sputtered on the surface, then exposed through a photo maskwith a pattern of a gate electrode G, and developed to form a gateelectrode G shaped photoresist layer. The developed material wasimmersed in an etching liquid such as cerium ammonium nitrate to removethe Cr film in the portions other than the photoresist layer formed,followed by removal of the resist layer to form the gate electrode G(FIG. 1 a).

Subsequently, a light sensitive organic insulation layer was formedemploying a sputtering method to form a gate insulation layer IF with athickness of 500 nm (FIG. 1 b).

Subsequently, a lift off resist was coated on the gate insulation layerIF, and subjected to patterning via a photolithographic method, followedby forming a 5 nm thick Cr film and a 50 nm Au film in that order via asputtering method. After that, the resulting material was subjected toultrasonic washing in dimethylformamide at room temperature to remove anunnecessary lift off resist, whereby a source electrode S and a drainelectrode D were formed (FIG. 1 c). The channel length or a distancebetween the source electrode S and the drain electrode D was 10 μm, andthe channel width was 100 μm.

Subsequently, a liquid repellent bank material available on the market(NPAR-502, produced by NISSAN CHEMICAL INDUSTRIES LTD.) was coated onthe basal plate P with the gate electrode G, the gate insulation FilmIF, the source electrode S and the drain electrode D formed, employing aspin coat method, and subjected to patterning via a photolithographicmethod to form a bank layer BK (FIG. 1 d).

In the above patterning, an opening BKa with a size of 20 μm×100 μm wasprovided on the channel at a pitch of 141 μm, and an opening BKb with asize of 10 μm×10 μm was provided on an area extending from the drainelectrode D and corresponding to the connecting terminal Da. A grooveBKc surrounding the opening BKb was provided at a position 5 μm distantfrom the opening BKb. The center of the channel and the center of theconnecting terminal Da were positioned diagonally so that the centers ofthe channels and the centers of the connecting terminals Da form azigzag pattern.

Subsequently, the ink IK, in which 6,13-bistriethylsilylethynylpentacenewas dissolved in tetrahydronaphthalene in an amount of 3% by weight, wasjetted into the opening BKa of the bank layer BK formed on the channel,employing a piezoelectric ink jet printing process to form an organicsemiconductor layer SF (FIG. 3 e).

Thus, an organic TFT 1 was manufactured. The organic TFT 1 was observedthrough an optical microscope and AMF (produced by KEYENCE CO., LTD.).As a result, it has proved that the ink IK did not flow into theconnecting terminal Da extending from the drain electrode D, and theorganic semiconductor layer SF with an average thickness of 50 nm wasformed with high accuracy on the channel.

EXPLANATION OF THE SYMBOLS

-   -   1: ORGANIC TFT (ORGANIC THIN FILM TRANSISTOR)    -   1A: ORGANIC TFT ARRAY    -   BK: BANK LAYER    -   BL: BUSLINE    -   D: DRAIN ELECTRODE    -   E: PIXEL ELECTRODE    -   G: GATE ELECTRODE    -   HF: PLANARIZED LAYER    -   IF: GATE INSULATION LAYER    -   IK: ORGANIC SEMICONDUCTOR SOLUTION (INK)    -   PF: PASSIVATION LAYER    -   S: SOURCE ELECTRODE    -   SF: ORGANIC SEMICONDUCTOR LAYER    -   P: BASAL PLATE

The invention claimed is:
 1. A method of manufacturing an organic thinfilm transistor, the method comprising the steps of: preparing a basemember; forming a source electrode and a drain electrode with a channeltherebetween on the base member; forming a bank layer on the basemember, the bank layer having a first opening on the channel and asecond opening on a predetermined area on the base member, the firstopening being at a different position from the second opening, and thebank layer having a groove or grooves formed in a surface of the banklayer at a position between the first opening and the second opening;and applying an organic semiconductor solution on the channel throughthe first opening to form an organic semiconductor layer on the channel,wherein the predetermined area is an area into which the organicsemiconductor solution is not to flow, and wherein the groove or groovesare configured to prevent the semiconductor solution from getting acrossthe groove or grooves from a side of the first opening and flowing intothe second opening when the semiconductor solution having been appliedon the channel flows on a surface of the bank layer from the channel andspreads towards the second opening.
 2. The method of claim 1, whereinthe organic semiconductor solution is applied by an ink jet process. 3.The method of claim 1, wherein the bank layer is to formed of a materialhaving liquid repellency against the organic semiconductor solution. 4.The method of claim 1, wherein the groove is formed to surround thesecond opening.
 5. The method of claim 1, wherein a plurality of thegrooves are formed.
 6. The method of claim 1, wherein the first openingand the second opening are positioned diagonally on the base member. 7.The method of claim 1, wherein the predetermined area is an area where aconnecting terminal extending from the source electrode or the drainelectrode is provided.
 8. The method of claim 7, further comprising thestep of: forming a pixel electrode to be connected with the connectingterminal through the second opening.
 9. The method of claim 1, furthercomprising the step of: forming a passivation layer on the organicsemiconductor layer.
 10. The method of claim 1, wherein the organic thinfilm transistor is a bottom gate type thin film transistor and the basemember comprises a basal plate, a gate electrode formed on the basalplate and a gate insulation layer to cover the gate electrode.
 11. Themethod of claim 10, wherein the groove is formed by raising a part ofthe bank layer, the part being raised by a part of the gate insulationlayer underneath the bank layer, the part of the gate insulation layerbeing raised by a wiring pattern provided underneath the gate insulationlayer.
 12. The method of claim 1, wherein the organic thin filmtransistor is a top gate type thin film transistor and the base membercomprises a basal plate.
 13. An organic thin film transistor comprising:a basal plate; a gate electrode formed on the basal plate; a gateinsulation layer formed on the gate electrode; a source electrode and adrain electrode with a channel therebetween, said source electrode andsaid drain electrode being formed on the gate insulation layer; a banklayer having a first opening on the channel and a second opening on apredetermined area on the basal plate, the first opening being at adifferent position from the second opening and the bank layer having agroove or grooves formed in a surface of the bank layer at a positionbetween the first opening and the second opening; and a semiconductorlayer formed by applying an organic semiconductor solution on thechannel through the first opening, wherein the predetermined area is anarea into which the organic semiconductor solution is not to flow, andwherein the groove or grooves are configured to prevent thesemiconductor solution from getting across the groove or grooves from aside of the first opening and flowing into the second opening when thesemiconductor solution having been applied on the channel flows on asurface of the bank layer from the channel and spreads towards thesecond opening.
 14. The organic thin film transistor of claim 13,wherein the groove is formed around the second opening.
 15. The organicthin film transistor of claim 13, wherein the predetermined area is anarea where a connecting terminal extending from the source electrode orthe drain electrode is provided.
 16. The organic thin film transistor ofclaim 13, further comprising: a pixel electrode to be connected with theconnecting terminal through the second opening.
 17. An organic thin filmtransistor comprising: a basal plate; a source electrode and a drainelectrode with a channel therebetween, said source electrode and saiddrain electrode being formed on the basal plate; a bank layer having afirst opening on the channel and a second opening on a predeterminedarea, the first opening being at a different position from the secondopening, and the bank layer having a groove or grooves formed in asurface of the bank layer at a position between the first opening andthe second opening, a semiconductor layer formed by applying an organicsemiconductor solution on the channel through the first opening, a gateinsulation layer formed on the semiconductor layer; and a gate electrodeformed on the gate insulation layer, wherein the predetermined area isan area into which the organic semiconductor solution is not to flow,and wherein the groove or grooves are configured to prevent thesemiconductor solution from getting across the groove or grooves from aside of the first opening and flowing into the second opening when thesemiconductor solution having been applied on the channel flows on asurface of the bank layer from the channel and spreads towards thesecond opening.
 18. The organic thin film transistor of claim 17,wherein the groove is formed around the second opening.
 19. The organicthin film transistor of claim 17, wherein the predetermined area is anarea where a connecting terminal extending from the source electrode orthe drain electrode is provided.
 20. The organic thin film transistor ofclaim 19, further comprising: a pixel electrode to be connected with theconnecting terminal through the second opening.
 21. The method of claim1, wherein the groove extends through the bank layer or is anindentation in a surface of the bank layer.
 22. The method of claim 1,wherein a wall of the groove is configured to prevent flow of theorganic semiconductor solution into the groove or grooves when thesemiconductor solution flowing on the surface of the bank layer from thechannel arrives at the wall of the groove.
 23. The method of claim 13,wherein the groove extends through the bank layer or is an indentationin a surface of the bank layer.
 24. The method of claim 13, wherein awall of the groove is configured to prevent flow of the organicsemiconductor solution into the groove or grooves when the semiconductorsolution flowing on the surface of the bank layer from the channelarrives at the wall of the groove.
 25. The method of claim 17, whereinthe groove extends through the bank layer or is an indentation in asurface of the bank layer.
 26. The method of claim 17, wherein a wall ofthe groove is configured to prevent flow of the organic semiconductorsolution into the groove or grooves when the semiconductor solutionflowing on the surface of the bank layer from the channel arrives at thewall of the groove.